1. Field of the Invention
The present invention generally relates to a microstructural polarized light-guide device, more particularly, a nano-scale light-guide device which is composed of subwavelength polarization beam splitter structure, polarization conversion module, and light-guide module.
2. Description of the Prior Art
With reference to FIG. 1, which illustrates a side view showing a conventional back light structure. As shown in the figure, a back light module 1 mainly comprises an incident CCFL (cold cathode fluorescent lamp) 10, a reflection shade 9, a light-guide plate 7, a reflection plate 5, a diffusion plate 11, a prism plate 12A, a prism plate 12B, and an absorbing polarizer 13. Light emitted by the CCFL 10 or reflected by the reflection shade 9 may directly or indirectly enter into the light-guide plate 7 for propagation. Light passing through an optical-designed structure located at the lower portion of the light-guide plate 7 and reflected by the reflection plate 5 is interfered. Continuously, the light is diffusely emitted with a certain angle to the light-guide plate 7 and averagely distributed on a lighting area. Then the diffusion plate 11, the prism plate 12A and the prism plate 12B adjust the emergence angle of the light so as to let the emergence direction of the light be vertical to the absorbing polarizer 13. Before the light entering into a liquid crystal layer, the light is polarized by the absorbing polarizer 13, and the energy of the light is then decreased about 50%. So that the usage to the light is not expectable.
For all elements, the light-guide plate 7 is a propagation media of the back light module 1. The shapes and optical structures of the light-guide plate 7 are the solutions to the brilliance of a emergence surface and the distribution performance of the emergence light. Due to that of polarized light being effectively used by an LCD and a light-guide device being with the function of polarization, the light absorbed by the absorbing polarizer 13 can be recycled in order to promote the usage of light. Further, light can be concentrated to emit, and the direction of the emergence light is almost vertical to the absorbing polarizer 13.
In addition, while the application range of the TFT color LCD is being increased, the volumes of the TFT color LCD and the related consumer electronic products are being slim, and the advantages of the TFT color LCD, such as high illumination, uniformity and wide-angle, are being achieved, many different fields are doing their best to developing the back light system in order to make it step into a further stage.
According to ROC Patent No. I266117 of a back light module with polarized light conversion function, a light-guide plate is disposed on a phase retarder, comprising a plurality of microstructures on the surface. The light source is placed at the edge of the light-guide plate, light is extracted by the microstructural surface of the light-guide plate. In addition, a plurality of strip-shaped subwavelength gratings are disposed on the light-guide plate to allow P-polarized light to emerge from the light-guide plate and allow S-polarized light to be recycled.
S-polarized light is reflected through a reflector sheet on the bottom of the back light module and is converted into P-polarized light by passing through the phase retarder twice, to pass through the subwavelength gratings. The prior art recycles S-polarized light to improve the TFT LCD display efficiency, in addition, enable a more light-weighted back light module by applying the plurality of strip-shaped subwavelength grating structure.
To meet the light-weight and energy saving LCD for consumers, and to achieve more simple and efficient production processing, the present invention provides a microstructural polarized light-guide device, i.e., a nano-scale polarization beam splitter structure and a polarization conversion module, in order to improve the optical efficiency of the back light module by re-utilizing reflected polarized light beams. The invention, therefore, is a light-weighted device with lower energy consumption.